The disclosure relates to gas treatment devices and, more particularly, to an apparatus and method for improving gas treatment device performance.
The reduction of emissions from vehicle exhaust systems is a well known problem. As the number of vehicles having an internal combustion engine continues to increase, the problem is becoming more severe and despite the introduction of gas treatment device exhaust systems, the exhaust emissions from vehicles fitted with such systems are still relatively high.
In particular exhaust emissions are relatively high during the initial start up or warm-up phase, also referred to as the xe2x80x9ccold startxe2x80x9d, of an internal combustion engine after starting, especially with regard to the emissions of carbon monoxide, oxides of nitrogen and hydrocarbons. Start up conditions refer to when the gas treatment device is not operating. For example, this could be on a cold winter day when the temperature is xe2x88x9210xc2x0 C. or on a summer day when the ambient temperature is 30xc2x0 C. The gas treatment device must be heated to approximately 250xc2x0 C. before it becomes operable to convert the combustion by-products of the internal combustion engine. Normal operating temperature is in the 400xc2x0 C. to 800xc2x0 C. range. For the internal combustion engine to meet the Federal Test Procedure for the new stringent exhaust requirements, the catalyst must come up to temperature as quickly as possible.
The particularly high exhaust emissions are largely due to the fact that the gas treatment device has not reached its so-called xe2x80x9clight-offxe2x80x9d temperature, at which the catalyst causes the required catalytic reactions to take place. The light-off temperature can be defined as the temperature at which the gas treatment device reaches 50% conversion. Modem catalyst systems start operating at temperatures of around 200xc2x0 C. to 300xc2x0 C.
In order to reduce the quantity of harmful emissions during the initial warm-up phase, a plurality of different solutions has been proposed, many of these solutions being based on shortening the time taken to reach the light-off temperature by raising the temperature in the catalyst as fast as possible. During start up, this can be achieved by generating increased heat energy into the exhaust system, which subsequently causes the catalyst to be rapidly heated.
A previously known arrangement for obtaining this reduction in time for the light-off temperature to be reached is one comprising an electrically heated catalyst, which is arranged upstream from the main catalyst. However, this arrangement implies certain drawbacks. Firstly, the cost for a heatable substrate is considerable. Furthermore, the consumption of electrical energy is relatively high. An additional power supply such as an extra battery may be required in the vehicle. Also, the durability of the electrically heatable substrate may constitute a problem.
A gas treatment device comprises a substrate, a shell concentrically disposed around the substrate, and a mat support material disposed between the substrate and shell. A variable flow regulator assembly is in fluid communication with the substrate. The variable flow regulator assembly comprises a second portion having a coefficient of thermal expansion greater than a first portion coefficient of thermal expansion. The second portion is disposed between a first portion and the substrate.
A method for using a gas treatment device in a gas treatment system comprises introducing a gas into the gas treatment device. The gas treatment device comprises a shell concentrically disposed around a substrate, a mat support material disposed between the substrate and shell, and a variable flow regulator assembly in fluid communication with the substrate. The variable flow regulator assembly comprises a second portion having a coefficient of thermal expansion greater than a first portion coefficient of thermal expansion, and the second portion is disposed between a first portion and the substrate. The gas passes through the variable flow regulator assembly. The flow distribution of the gas is changed to the substrate.
A gas treatment device comprises a means for containing a substrate, with a means for supporting the substrate disposed therebetween; a means for controlling fluid flow distribution to the substrate comprising a variable flow regulator assembly comprising a second portion having a coefficient of thermal expansion greater than a first portion coefficient of thermal expansion, wherein the second portion is disposed between a first portion and the substrate; and a means for connecting the means for containing to a fluid supply, wherein the means for connecting is in operable communication with the means for controlling fluid flow distribution.
A catalytic converter comprises a shell concentrically disposed around a substrate comprising a catalyst, and a mat support material disposed between the substrate and shell. A variable flow regulator assembly is placed in fluid communication with the substrate. The variable flow regulator assembly comprises a second portion having a coefficient of thermal expansion greater than a first portion coefficient of thermal expansion. The second portion is disposed between a first portion and the substrate. A portion of at least the first portion is disposed around and fixedly attached to at least a section of the second portion. An end cone disposed concentrically around the variable flow regulator assembly is in operable communication with the shell, and in fluid communication with the variable flow regulator assembly.
The above described and other features are exemplified by the following figures and detailed description.